There exist numerous situations in which it is desirable to implant or position electrodes at specific locations within the body. In some situations it is desirable to pass electrodes into the body through blood vessels or other body lumens in order to position the electrode in or near an organ or portion of the body that would otherwise be accessed only by open surgical means. However, allowing an electrode to remained positioned within a blood vessel or other body lumen may, in at least some cases, be less than desirable. Accordingly, there exists a need in the art for devices and methods to facilitate advancement of an electrode through a body lumen to a location near the tissue or organ in which the electrode is to be placed and, thereafter, to cause the electrode to travel outside of that body lumen in into the desired tissue or organ parenchyma. The present invention satisfies such need.
One of the many applications in which transluminal/interstitial electrode placement is desirable is for placing pacing electrodes within myocardial tissue. At present, it is common for physicians to transvenously insert pacing wires into coronary veins for the purpose of treating cardiac rhythm disturbances. This allows the electrode to float freely in the coronary vein and the electrode does not become interstitially implanted within myocardial tissue. Recently, a technique known as “cardiac resynchronization therapy” (CRT) has been used for the treatment of congestive heart failure. CRT involves pacing of both left and right ventricles to enhance the heart's pumping efficiency. In a recent 12-month study conducted in Europe and Canada, it was concluded that the administration of CRT using the Medtronic InSync® system resulted in decreased fatigue and increased exercise tolerance for as long as one year following CRT.
In general, CRT utilizes an implantable pacemaker-like device that delivers electrical impulses to resynchronize the beating action of the heart's chambers. This implantable pacemaker-like device is implanted subcutaneously in the pectoral area. Two (2) endocardial leads which are placed in the right atrium and right ventricle and a third epicardial lead is placed transvenously within a coronary vein located on the outside of the left ventricle. It has heretofore been the practice to allow the epicardial pacing lead (i.e., a wire having an electrode at its distal tip) to float freely within the lumen of a coronary vein located on or near the epicardial surface of the left ventricle. However, the use of such free-floating epicardial pacing electrode can be less than advantageous because a) the electrode can migrate or move through the lumen of the coronary vein b) the electrical pacing impulses delivered by that epicardial lead must be sufficiently strong to pass through the wall of the coronary vein and through adjacent myocardial tissue to reach the area within the myocardium where the impulse actually causes the desired myocardial muscle fibers to contract and c) where the electrode can be placed within the venous anatomy intraluminally may not be the most optimal myocardial location for electrical stimulation. If this epicardial electrode were to be positioned within the myocardial tissue at or near its intended site of action, instead of in the lumen of a coronary vein, the potential for migration of the electrode and the amount of current required to be delivered through the electrode would be minimized.
In addition, there exists a technique known as “neuromodulation” (NMT), in which electrodes are placed into areas of the brain and connected to permanently implantable stimulators. MNT has been used to treat disorders such as spasticity, pain, epilepsy and Parkinson's disease as well as several other neurological conditions. Other organs in which the transluminal/interstitial electrode placement of the present invention may have benefit include but are not limited to the gastrointestinal tract, kidney, carotid body or other vascular structures, bladder, skeletal muscle, spinal cord, nerves, respiratory tract, olfactory apparatus and the eye.